1. Background
This invention relates to systems which sense spatial relationships and to the individual sensors used in the systems. The system is capable of producing a decision based on the values of one or more sensors. The system finds application in a variety of gesture recognition applications, exemplified by communication devices for nonvocal deaf or deaf-blind individuals. The system also finds application providing information on complex animate and inanimate motion which can be stored and/or processed immediately to construct a true or transformed model of the original motion. The model may be used to analyze the original motion or used as a control input to a second application.
There are various methods of sensing spatial relationships of interrelated parts, such as human and robotic joints and other moveable parts. In particular, there is a strong interest in improving on and developing new goniometric, i.e., angle measuring, devices. Commonly used goniometers, such as optical encoders, resolvers, potentiometers, Hall-effect sensors, and the like, are based on optical, electrical, mechanical and electromechanical technologies, etc. Most available goniometers are housed in bulky mechanical structures which can be difficult to mount and often interfere with the motion they are intended to track. The devices can be expensive, have limited resolution and can be difficult to use in a case where the bend axis is not rigidly defined and varies during flexure (e.g., a finger joint).
There is therefore a need for a low-profile, high resolution goniometer which is easily and unobtrusively mounted to a surface to monitor angles between two or more moveable structures associated with that surface (e.g., to monitor the bending of a joint or hinge, or the interrelation between the angles of a number of joints or hinges). The output of such a goniometer may be used to control the movement of computer generated objects or figures on a computer monitor, as well as to control the operation of physical machinery, and the like.
2. Relevant Literature
U.S. Pat. No. 4,414,537 describes an instrumented glove which uses optical bend sensors, while U.S. Pat. Nos. 4,414,537 and 4,542,291 describe an instrumented glove using related optical sensing technology. Instrumented gloves are described by Foley, xe2x80x9cInterfaces for Advanced Computing, xe2x80x9cScientific American, October, 1987, pp 127-135. A strain gage flex sensor is described in Jesperson, et al., xe2x80x9cJoint Angle Position Sensor,xe2x80x9d 40th ACEMB, Niagara Falls, N.Y., Sep. 10-12, 1987, p 104. A Hall-effect sensor used to measure finger joints is described in Marcus, et al., xe2x80x9cSensing Human Hand Motions For Controlling Dexterous Robots,xe2x80x9d 2nd Annual Space Operations Automation and Robotics Workshop, Wright State Univ, Jul. 20-23, 1988.
Sensors and sensor arrays are provided where each sensor is characterized by having at least one flexible variable resistance strain sensing element mounted to a flexible backing. In one embodiment the sensor motion is restricted by a guiding element and at least one end of the sensor is able to slide relative to the guiding element material. The guiding element is affixed to a surface and the sensor is guided by the guiding element to produce an electrical signal representative of the angle between two structures related to the surface. A plurality of sensors can be used to measure the conformation of the surface at a plurality of points.
Adaptive finger-gesture recognition algorithms are also provided where various pre-defined hand formations are recognized from continuously varying finger motion. Both a Bayesian and an artificial neural network classifier are described which select the appropriate gesture in conjunction with a dynamic gesture parsing routine.